Date Approved

3-21-2019

Embargo Period

3-27-2019

Document Type

Dissertation

Degree Name

PhD (Doctor of Philosophy) in Engineering

Department

Chemical Engineering

College

Henry M. Rowan College of Engineering

Advisor

Stanzione III, Joseph F.

Committee Member 1

Dahm, Kevin

Committee Member 2

Vernengo, Andrea J.

Keywords

Bio-based, Lignin, Lithium-ion batteries, Polymer electrolytes, Thiol-ene

Subject(s)

Lithium ion batteries

Disciplines

Chemical Engineering

Abstract

Industrial and consumer demand for smaller and safer technologies motivates a global research effort to improve electrolytic polymer separators in lithium-ion batteries (LIBs). To incorporate the aromatic structural advantages of lignin, an abundant and renewable resource, into polymer electrolytes, molecules that can be derived from lignin are functionalized and UV-polymerized with multifunctional thiol monomers. Monomer aromaticity, thiol molecular weight, and total functionality are varied, allowing for analysis of the relationships between polymer structure and electrochemical properties.

The synthesized polymers display conductivities on the order of 10^-5 S/cm for gel polymer electrolytes and 10^-4 S/cm for solid polymer electrolytes, comparable to the state of the art. Conducting ability is improved with lower polymer Tg and crosslink density. However, the larger crosslink densities of polymers containing higher aromatic content and higher total functionality favor specifically cationic transport, a desirable feature for LIB polymer electrolytes. Assembly in coin cells reveals the need for reduced ion aggregation in the polymers and improved contact at the electrolyte-electrode interface. Efforts to address these concerns are attempted and future work is discussed. The conducting abilities of the bio-based polymer electrolytes in this study prove the viability and advantages of lignin-derived feedstock for use in LIB applications and reveal structurally and thermally desirable traits for future work.

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